1. Field of the Invention
The present invention relates to a fluid-operated press, and in particular, to a pneumatic press actuated by a combination of a piston and a cylinder for driving a ram plate.
2. Scope of the Prior Art
Fluid-operated presses are used in many applications, e.g., in stamping metal parts. Conventional presses include a ram head mounted for vertical sliding movement on a plurality of vertical guide posts upstanding from the stationary bed. The ram head and the stationary bed typically define a die-set area therebetween. An upper plate is usually secured to the upper ends of the guideposts to maintain the latter in vertical alignment, thereby permitting free sliding movement of the ram plate.
In certain instances, the ram head is fluid actuated by a piston and cylinder arrangement located above the upper plate with a piston rod extending therethrough to drive the ram head downwardly into the die-set area, the ram head being mechanically returned by springs or the like. In other arrangements such as that disclosed in U.S. Pat. No. 3,450,037 to Lickliter et al., a piston and cylinder operable at low pressures is arranged between the upper plate and the ram head to directly drive the ram head.
It is also known to use an air bladder arranged between the upper plate and the ram head to directly drive the ram head instead of a piston and cylinder. Such equipment is typically adapted to be operated at high speed, providing repetitive reciprocations of several hundred per minute.
Existing pneumatic presses typically operate at a very high noise level, with significant vibration and consequent wear on the parts. Moreover, the pneumatic hydraulic drive equipment and the return springs are typically provided above the work surface which necessarily contributes a significant height to the equipment. If there is a jam at the work surface, the difficult and laborious process of disassembling all of the equipment above the work surface adds significant cost to operating the equipment. Furthermore, the exposed return springs and other operating parts above the work surface present a risk of injury to the operator.